1. Field of the Invention
The invention relates to an apparatus and method for detecting the surface profile of a test object.
2. Description of the Related Art
FIGS. 1 and 2 illustrate a conventional Michelson-type interferometric apparatus that includes a light source 90, a beam splitter 81, a reflective component 82, a sensor 94, a carrier 93, and a computing device 96.
The conventional method for detecting the surface profile of a test object 70, such as semiconductor wafers and glass substrates for liquid crystal display applications, with the use of the aforementioned conventional interferometric apparatus includes the following steps:
a) enabling the light source 90 to emit a white light beam (I);
b) through a beam splitter 81, dividing the light beam (I) into a reference beam (Ir) that is directed to the reflective component 82, and a probing beam (Io) that is directed to a scanned segment of the surface of the test object 70 on the carrier 93;
c) through the beam splitter 81, combining the reference beam (Ir) reflected by the reflective component 82, and the probing beam (Io) reflected by the scanned segment of the surface of the test object 70 to result in a heterodyne light beam;
d) enabling the sensor 94 to convert the heterodyne light beam into a corresponding electrical signal;
e) enabling the computing device 96 to record the electrical signal converted in step d);
f) moving the beam splitter 81 and the reflective component 82 in a scanning direction, as indicated by arrow (S2) in FIG. 2, thereby varying the optical path length of the probing beam (Io) to result in another heterodyne light beam for the scanned segment in step c) when steps a) to e) are repeated;
g) enabling the computing device 96 to analyze the electrical signals recorded therein to determine the surface profile at the scanned segment of the test object 70; and
h) moving the carrier 93 in another scanning direction, as indicated by arrow (S1) in FIG. 1, and repeating steps a) to g) to determine the surface profile of another scanned segment of the surface of the test object 70.
The aforementioned conventional method is disadvantageous in that the beam splitter 81 and the reflective component 82 are required to be moved in the scanning direction (S2) in order to determine the surface profile of a scanned segment of the test object 70. The process as such results in a slow scanning speed, and has a detrimental affect upon the efficiency of the surface profile detection operation.